The present invention relates to a drive device incorporating a hydraulic motor and a planetary reduction gear, the motor comprising a housing inside which is disposed a cylinder block with radial pistons, the device comprising means for coupling between the output of the motor and the input of the reduction gear, the latter comprising a housing inside which is disposed a planetary reduction gear system and having an output provided with means for driving in rotation.
A drive device of this type may, for example, be used for driving a concrete mixer, the output of the reduction gear forming drive shaft for the drum. Such a device may also be used for driving machines such as grinders, winches, mixers (for example for the chemical or food industry), or for systems of translation. In such situations, the output of the reduction gear is adapted to the different uses.
EP 0 482 660 discloses a device of this type, in which the housing of the motor and the housing of the reduction gear are separated by sealing means. Insofar as the degree of cleanliness of the fluid required for the hydraulic motor is greater than that required for the planetary reduction gear, such separation makes it possible to avoid that a possible pollution of the fluid contained in the housing of the reduction gear, due for example to wear of the teeth of the gears contained in this housing, reaches the housing of the motor. On the other hand, such separation renders necessary two distinct sources of fluid, connected to the two housings by distinct circuits, in which the fluid pressure must be controlled by appropriate means.
WO 94/23918, for example, also discloses a drive device in which the housing of the motor and that of the planetary reduction gear form one and the same enclosure. This arrangement presents the advantage of requiring only one source of fluid for this common enclosure but, on the other hand, it presents the risk of a pollution of the fluid, due for example to wear of the reduction gear, contaminating the interior space of the motor housing.
It is an object of the present invention to improve the known device of the type mentioned above.
This object is attained with the device of the invention thanks to the fact that the housing of the motor and the housing of the reduction gear form distinct enclosures and that it comprises means for allowing a circulation of fluid between said housings and for controlling this circulation of fluid by limiting the circulation of fluid at least in one direction of circulation between the housing of the motor and the housing of the reduction gear.
Thanks to these arrangements, one and the same source of fluid is sufficient to feed the housing of the motor and that of the reduction gear.
From that standpoint, the invention presents the advantages of the devices in which the housing of the motor and that of the reduction gear are common.
However, the two housings are distinct and the circulation between them is controlled, which makes it possible for example to have different fluid pressures prevailing in the two housings or to arrange for only one of the two to be totally filled.
Thus, in that point of view, the device of the invention presents the advantages of the devices in which the housing of the motor and that of the reduction gear are isolated. In particular, the means for allowing a controlled circulation of fluid between the housing of the motor and the housing of the reduction gear may be chosen so as to ensure that the housing of the motor is filled permanently and that the pressure of the fluid in this housing does not exceed a predetermined value. For the fluid contained in the motor housing, the housing of the reduction gear may perform the role of an expansion vessel.
In addition, it will be noted that the means controlling the circulation of fluid may make it possible to avoid, or at least limit, the risks of a possible pollution inside the housing of the reduction gear being transmitted to the motor housing. For example, the control means may be made so as to prevent the impurities of dimension greater than a given dimension and found in the housing of the reduction gear, from penetrating into that of the motor.
According to one embodiment, the device comprises at least one conduit for circulation of fluid between the motor housing and the reduction gear housing, and said conduit is equipped with said means for limiting the circulation of fluid at least in one direction of circulation between the housing of the motor and the housing of the reduction gear.
These means are for example advantageously constituted by a restriction and/or by a non-return valve.
The device advantageously comprises a filling or a draining port, common to the housing of the motor and to the housing of the reduction gear, this port communicating with a filling or draining conduit common to said housings, and this filling or draining conduit forms a conduit for circulation of fluid between said housings.
This port and this conduit are therefore employed both for performing the function of filling or of draining of the housings and for allowing the controlled circulation of fluid between them, this limiting the number of machinings necessary for performing these two functions.
The filling or draining port is advantageously obturated by a stopper which cooperates with the means for controlling the circulation of fluid between the housings of the motor and of the reduction gear.
The housing of the motor and the housing of the reduction gear are advantageously separated by a separation wall, and the fluid circulation conduit is formed in this separation wall.
This arrangement renders the drive device particularly compact and simple. Moreover, it is inexpensive to manufacture.
According to an advantageous arrangement, the device comprises a first and a second conduit for circulation of fluid between the motor housing and the reduction gear housing, the first conduit cooperating with a first non-return system which allows the circulation of the fluid only in the direction going from the reduction gear housing towards the motor housing, while the second conduit cooperates with a second non-return system which allows the circulation of the fluid only in the direction going from the motor housing towards the reduction gear housing, when the difference in pressure between said housings is at least equal to a given value.
A filter may be arranged on the first conduit to avoid the impurities located in the housing of the reduction gear penetrating into that of the motor. The first non-return system may be constituted by a conventional non-return valve. The second non-return system, which cooperates with the second conduit, makes it possible to maintain a sufficient fluid pressure in the motor housing. It is, for example, a non-return valve calibrated to a given pressure.
The first and second fluid circulation conduits are advantageously formed in the separation wall.
In certain applications, the drive device according to the invention may be fed in open circuit. This is the case for example for the motorization of a hauling winch.
However, it may be advantageous to use a closed circuit, for example for driving a concrete mixer drum. The fluid feed circuit of the drive device according to the invention is for example a closed circuit comprising a main pump which comprises a housing, presenting two main suction or delivery ports and which is intended to feed a main circuit comprising main feed and exhaust conduits of the hydraulic motor, the circuit further comprising a booster pump having a main suction port connected to a fluid reservoir.
In this circuit, the fluid reservoir is advantageously constituted by the housing of the hydraulic motor.
The booster pump serves to maintain in the circuit a sufficient fluid pressure to avoid the phenomena of cavitation. The circuit is simplified by the fact that the fluid reservoir from which the booster pump draws the booster fluid is directly constituted by the housing of the hydraulic motor. It is therefore unnecessary to provide a reservoir in the form of a separate enclosure. The number of components of the circuit is thus limited and the assembly is very compact.
This circuit further comprises an exchange or replenishing unit adapted to draw fluid from the main circuit and means for returning cooled fluid to the reservoir constituted by the housing of the hydraulic motor.
The exchange or replenishing unit is advantageously integrated in the housing of the main pump and is directly connected to said housing, to inject thereinto the fluid drawn from the main circuit, without a conduit outside said housing; moreover, the housing of the main pump is connected to the housing of the hydraulic motor by a pipe for return of fluid towards said housing of the hydraulic motor, on which cooling means are disposed.
The exchange unit draws fluid from the main circuit and injects it into the housing of the main pump. The fluid is drawn from the main circuit, upstream of the ports for connection of the pump to the main conduits of the motor. In this way, no outside conduit is necessary either for drawing the fluid or for injecting it into the housing of the main pump. The drawing and injection circuit is therefore extremely short. For cooling the motor, the fluid is drawn from the housing of the pump and is injected into the housing of the motor after having been cooled. In this way, the exchange circuit allows both the motor housing and the pump housing to be flushed.